The transformation of light energy into electrical energy using photovoltaic cells has been known for a long time and these cells are currently used in various electronic devices such as watches, calculators, cameras and the like.
These cells can be divided into four main types, namely metal-semiconductor (MS) junction cells of the Schottky diode type, metal-insulator-semiconductor (MIS) junction cells, semiconductor-insulator-semiconductor (SIS) junction cells, and homojunction or heterojunction cells.
The term junction is understood to mean the transition zone between a metal and a semiconductor or between two semiconductors of different types of conductivity.
In all known thin layer photovoltaic cells the semiconducting material used is always deposited in the form of a thin continuous and smooth layer on the surface of a substrate previously covered by a first transparent electrode made, for example, of metal. This layer of semiconducting material is then covered, depending on the type of cell, by one or more layers (semiconducting and/or insulating and/or conducting), the upper most layer forming the second electrode.
Although developments and improvements have been made to these photovoltaic cells over the last few years to improve their efficiency, this efficiency still remains relatively modest.
Moreover, the manufacture of these cells requires the use of materials of great purity and thus the use of sophisticated equipment installed in clean rooms, so that these cells still remain difficult to produce.